Thermostat.



PATENTED MAY 19, 1908.

C. J. LETZING.

THBRMOSTAT. APPLICATION FILED FEB. 2a, 1967.

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CHRISTIAN J. LETZING, OF BOSTON, MASSACHUSETTS.

THERMOSTAT.

Specification of Letters Patent.

Patented May 19, 1908.

Application filed February 28, 1907. Serial No. 359,810.

system, and it consists in a thermostat which is protected fromcorrosion, dust and the other incidentals of a factory or other placewhere thermostats are used which render the thermostat imperfect anduncertain in its working so that full reliance cannot be placed .upon itas a circuit closer to close a circuit onlyat the time needed.

My invention will be understood by reference to the drawings, in whichFigure 1 is-a front elevation, and Fig. 2 a plan of athermostatembodying my invention. Fig. 3 is a longitudinal vertical sectionthereof. Fig. 4 shows a modification.

In each of these forms A is a yoke-shaped support or bracket ofinsulatin material which carries the terminals an adapted to be attachedto the ceiling of av room. It has two arms A A, each carrying .a bindingpost which are thus arranged oppo site each other, their opposing endsforming the terminals of a circuit.

B and C are the binding posts'which in the form shown in Figs. 1, 2 and3 are bored out at their opposing ends forming chambers as shown at and0. Each bindin post is attached to its arm A bymeans 0 a screw b and cwhich passes through it and the arm A to which it is attached so that itwill not be moved when the binding screw is screwed to hold the circuitwire in place. It has the usual bindin screw VI; and c by means of whichthe wires D forming part of thecircuit are attached to the thermostat.Each bindin post carries an annulus E preferablg of ample, ard rubber,which fits 'bver the inner end of the binding post, the diameter of theopening in its outer end being enlarged sufficiently to receive and holda casing F preferably made of glass, which-is thus held permanently inplace. flhe shape of the.

casing in cross section is immaterial 'so long as the lower nner surfaceof the chamber forined thereby willYco-act'with the fusible which is.

insulating material, for eX- terial so long as it is in itself aconductor of electricity and fusible at a predetermined degree oftemperature. This pin G and the washer 9 it will be noted, although theyproject from the binding post B, do not enga c with the binding 0st C soas to form an e ectrical contact t erewith, but the washer containssuflicient metal so that when melted it will run into the bottom of thechamber formed by the tube F and will s read over what might be termedthe floor of the chamberformed by this tube and consequently will makeelectric contact with the terminals of the binding posts thusclosing thecircuit through them. By this means the circuit is closed when the heatin the room has reached the danger point and the necessary alarm isgiven at the central station.

I have-found that this construction is exceedingly valuable-because thevarious working arts, the terminals, fusible metal, etc., of t eapparatus,- being inclosed within this chamber, are protected from theyarious conditions, atmospheric and' otherwise, which cause apparatus ofthis kind to corrode and lose their efficiency in time. Thus in myconstruction the terminals'of the posts are maintained in a far bettercondition, bri hter and cleaner, than they would be in a amp room, andthe appara us will not collect the dust or lint with whic the air insome mills is apt to be filled. Moreover where a glass tube is used as acasing to form the chamber the condition of the thermostat may beexamined from time to time without taking it apart. I The tube should beof insulating material or at least should be insulated from the bindingposts .and at the same time should be of such character as to transmitheat easily through its walls.

In Fig. 4 I have shown a modification of this construction in which theparts are inclosed in the chamber as above described, but in thiscasethe fusible metal washer g ,insteadof forming a part of theelectrical Fig. 4 becomes more or less corroded and so prefer that theterminal of the-post C shall be pointed as shown at c. When the washer gmelts the spring H is released so that it expands and engages or wrapsitself around the point 0 of the post C, thus forming a good contact andclosing the circuit. For a thermostat of this character, that is one inwhich the spring construction is used, I find that the inclosing of thearts in a protecting chamber is of especia im ortance as when exposed tothe air, especial y in a damp room, the surface of such a spring as isshown in cannot be expected to make such a perfect electrical contact aswhen it is fresh and clean. It is evident that this application of achamber to thermostatic use is of considerable value and that it may beused to inclose other automatic circuit closers than that shown. Theshape in which I use the fusible metal and the way in which I support itare simple and very effective and these elements combine to make athermostat of great practical value. Moreover another advantage of theform of thermostat which I have shown in Fi s. 1, 2 and 3 is that whenthe fusible meta of the thermostat has once been melted the thermostatthereafter may be taken down, the metal remelted over a lam and thethermostat being held in 'a' vertica posi tion the melted metal will rundown into the chamber in the binding post B and the thermostat will thenbe in condition to use a ain for when the thermostat is again putinp aceand submitted to a high degree of tem erature sufficient to meltthe-metal it wil run out from the chamber and make contact as before.

fusible metal in a form of'a washer to t this is by no means necessaryto accomp ish While it is convenient when the thermostat is firstconstructed to apply the e in,

line, one of said terminals carrying a fusiblewasher adapted when fusedto cause the closing of the circuit between said terminals, asdescribed. a

2. A thermostat comprising two terminals located in substantially thesame horizontal line, one of said terminals carrying afusible washer, acasing surrounding said terminals whereby they may be protected fromcorrosion, said casing also servin thereof in electrical connection withboth terminals.

3. A thermostat comprising two terminals, a pin projecting from oneterminal, a washer of fusible material located on the said pin, andmeans adapted to cause the closing of the circuit between said terminalsupon the fusing of said material, as set forth.

4. In a thermostat, in combination, a casing, two binding posts formingterminals located in said casing, one of said binding posts having ahollow terminal end, a fusible circuit closer located between saidterminals in said chamber and adapted when melted to form a-contact withsaid terminals and thereafter when again melted to break contact and bereceived into the said hollow ter minal end as described. I

. CHRISTIAN J. LETZING. Witnesses:

M. E. FLAHERTY, M. V. FOLEY.

when said -washer has been melted to ho d the metal

